Thermally-operated multi-switch arrangement



Sept. 29, 1964 D. R. GRAHL THERMALLY-OPERATED MULTI-SWITCH ARRANGEMENT Filed Aug. 17, 1961 FIELL MKM United States Patent 3,151,229 THERMALLY-GPERATED MULTI-SWITCH ARRANGEMENT Darwin R. Grahi, Lincoln Park, Mich, assignor to American Radiator & Standard Sanitary Corporation, New

York, N.Y., a corporation of Delaware Filed Aug. 17, 1961, Ser. No. 132,058 11 Claims. 01. zoo-13s This invention relates to a thermally-operated multiswitch assembly, as for example an assembly which may be used in domestic heating systems to control the upper temperature limit produced by the heat producer and the cut-in or cut-out temperature of the heating medium circulator. In the case of air heating systems this type control is commonly referred to as a fan-limit control.

One object of the present invention is to provide an arrangement of thermal actuator and electric switches wherein the operating range of each switch may be accurately calibrated at the factory and wherein the actuation temperature of one of the switches may be varied as desired by the user.

A further object of the invention is to provide a thermal actuator-switch assembly wherein a minimum number of components makes up the assembly.

A further object of the invention is to provide a thermal actuator-electric switch arrangement wherein the components can be readily secured together in a single step operation.

Another object of the invention is to provide a thermal actuator-electric switch assembly wherein the operating parts of the assembly are effectively shielded from such dirt accumulations as would shorten the service life.

Another object is to provide. an actuator-switch assembly which utilizes trigger-equipped snap switches to provide precise switch actuation, desired contact pressure, lack of switch blade flutter, and operability in the presence of vibrational forces which are sometimes encountered in furnace operations.

A still further object of the invention is to provide a thermal actuator-electric switch assembly wherein triggerequipped snap switches are suitably disposed so that lead wires can be directly connected therewith without need for a terminal board and without danger of the lead wires becoming entangled against any of the switch parts.

A general object of the invention is to provide a thermal actuator-electric switch assembly which will have satisfactory operation and relatively low manufacturing cost.

Other objects of this invention will appear from the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

In the drawings:

FIGURE 1 is a sectional view of one embodiment of the invention taken on line 1-1 in FIG. 2;

FIG. 2 is a sectional view taken on line 2-2 in FIG. 1; and

FIG. 3 is a sectional View taken on line 3-3' in FIG. 2.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not Of limitation.

Referring to the drawings, there is shown therein a probe type control comprising a housing or casing structure including a base section 12 and a cover section 3,151,229- Patented Sept. 29,1964

14. Base section 12 comprises a base wall 16 having a foiwardly embossed or inset portion 18, a pair of forwardly extending flanges 20 and 22, a forwardly extending top wall 24 and a forwardly extending bottom wall 26. Cover section 14 comprises a front wall 28, a right side wall 30, and a left side wall 32, said side walls extending into close telescoping adjacency with the inner surfaces of the respective flanges 20 and 22, and the telescoped portions having cooperating detents 34 and recess-forming openings 36 for releasably retaining cover section 14 V on the base section 12. Upper and lower edges of the cover section walls are provided with short inturned flanges 33 to provide snug fits on the cooperating portions of the base section walls 24 and 26.

The cover section is U-shaped in horizontal cross section so that walls 30 and 32 may be readily flexed toward one another by manual grasping of the housing section in the palm of ones hand, with the users fingers pressing against wall 3% and with the users thumb pressing against wall 32. Because of this feature it is possible to readily separate the cover section from the base section; nevertheless the interfitting telescoping nature of the two sections is such as to cause them to be firmly retained to gether in service without rattling or unloosening.

Extending reaiwardly from the embossed portion 18 of base wall 16 is an elongated channel-like support or probe structure 38 of generally U-shaped cross section, said structure having a top wall 40, a right side wall 42 and left side wall 44, the lower edges of said walls 42 and 44 preferably being unconnected, and each of these walls having slots or apertures 46 therein to permit circulation of fluid through the structure. Referring to FIG. 1, the free end area of support structure 33 provides two facing support surfaces which mount the generally U- shaped bimetal 48. The bimetal has a relatively short web portion 50 and two relatively long preferably stiff fiat strip or leg portions 54 and 56, said strip portions having free ends extending through a base wall opening 58 into registry with the plunger type trigger operations 60 and 62 for the conventional snap switches 64 and 66. The terminals for the switches are shown at 67. It will be seen that lead wires for these terminals can be extended through a large opening in wall 26 without disturbance of housing section 14.

Bimetal strip 54 has mounted thereon a spring 68, the function of which is to vary the switch actuation temperature of said strip in a low temperature range. Factory calibration or adjustment of the operating temperature range for this bimetal strip is provided by the set screw element '70. A second set screw element 72 is provided for calibrating the. operating temperature of b-imetal strip 56, said screw elements preferably being cemented in place after the factory calibration operations.

Cooperating with spring leaf 68 in the temperature adjustment of strip 54 is a rotary member 74 having a shaft portion 76 thereof rotatably seated Within an opening in the web portion 78 of a generally U-shaped barrier or shield element 80. Referring to FIG. 3, the shield element comprises, beside the aforementioned web wall, an upper flange 82 and a lower flange 84, said upper flange having a short tab-like extension 86 fitting within a small opening in the base wall 16 to temporarily support the barrier in place within the housing for preventing improper aligning of parts during assembly operations. The central portion 855- of barrier wall 78 may be forwardly embossed to permit operative disposition of the cam portions 94 to be described hereinafter.

It will be noted that the aforementioned housing structure 38 is provided with laterally extending flanges 90 which scat against the rear face of base wall 16. Also, four headed rivet-type fasteners 92 are extended through flanges 90, base wall 16, respective ones of switches 64 and 66, and portions of barrier front wall 78 to secure the various components together as a rigid assembly. The front wall 73 seats semi-tightly on the faces of the switches, and the lateral edges of waHs 82 and d4 lie closely adjacent the side surfaces of the switches so that little if any fluid is able to flow from one side of base wall 16 to the other. In operation a semi-stagnant fluid area is established adjacent triggers 6t and 62 so that any dirt in the fluid stream bypasses this area instead of collecting therein. Also, the free ends of the bimetals are not contacted by high temperature fluid; consequently the major sensing is performed in the area adjacent screws 70 and '72. The bimetal movement per unit temperature change is fairly large, but there is good calibration of the bimetal strips in both the low and high temperature ranges.

Referring again to the construction of cam member 74, said member includes a cam portion 94 which is eccentric with respect to the axis of shaft portion 76, the arrangement being such that manual rotation of member 74 is effective to cause portion 94 to apply a lesser or greater force to leaf spring 68 in accordance with the position of rotational adjustment. The rotating operation may be performed by a twisting pressure applied to rectangular portion 98, said portion preferably having an angled edge 100 which forms a pointer cooperable with suitable temperature indicia on the front face of wall 28.

The illustrated device is intended to be used as a fanlimit control in a hot air heating system. In such use the bimetal 56 is intended to function as an upper limit control for de-energizing the heat producer when the heating medium reaches an abnormally high temperature, as for example 220 F. Bimetal 56 may take its illustrated position at about room temperature, and as the sensed temperature increases toward the high limit mark the free end portion of this bimetal will move toward trigger 62. The temperature at which the trigger will be moved to actuate its switch may be factory controlled by adjustment of screw element 72, inward threading of the screw element serving to raise the switch actuation temperature, and outward threading of the screw element serving to lower the actuation temperature.

In the described use stiff bimetal 54 is intended to control the heating medium circulator in a lower temperature range, as for example, 40 F. through 120 F. In calibrating the bimetal, member 74 may be rotated so that pointer surface 100 registers at a temperature indicia on wall 28 corresponding with the test temperature of bimetal 54. Screw element 70 may then be turned until the trigger 60 is actuated to snap the switch (either open or closed depending on the circuit and desired operational chmacteristics). During the initial calibrating movement of member 74 spring leaf 63 acts to apply a variable preload force onto the bimetal in accordance with the amount of counterclockwise rotational movement imparted to cam 94. The bimetal is thus stressed to the right by the preload force so that it develops a reaction force against spring 68 and cam 94 in a leftward direction. The bimetal is constructed so that temperature increase moves the free end of bimetal 54 to the right in opposition to the reaction force; cam d4 is contoured so that counterclockwise movement thereof from its FIG. 2 position causes it to apply an increasing pre-load force to the bimetal. Therefore, after calibration, counterclockwise movement of cam 94 results in lowering the switch tripping temperature; clockwise movement of cam 94 causes the switch to be operated at a relatively high temperature.

In the usual installation switch 64 is a normally open switch and is closed at high temperature; decreasing temperature moves bimetal 54 to the left to open the switch contacts. Rotational adjustment of cam 94 to increase the force of spring 68 requires that during cooling the bimetal must overcome a greater pre-load force before it can allow the internal springing in switch 64 to open the contacts to thus de-energize the fan or other heating medium circulator. The illustrated device is designed so that counterclockwise rotational adjustment of cam 94 will allow the fan to remain in operation during normal summer temperatures, as for example above 40 F.

It will be understood that while the above description has necessarily proceeded on the basis of a concrete embodiment of the invention, yet the invention is capable of practice in various forms and modifications as comprehended by the appended claims.

I claim:

1. In combination, a pair of generally flat parallel elon gated bimetal strips having fixedly mounted ends and free ends; a pair of trigger-equipped snap switches located adjacent the strip free ends, with the triggers thereof facing each other and with the free ends of the strips located therebetween; a separate mechanism for adjusting each strip so that the respective strips are enabled to independently actuate the respective switches in different and widely spaced temperature ranges; and means for varying the switch actuation temperature of one of the bimetal strips, including a stiff leaf spring mounted on said one bimetal strip and a rotary cam arranged to engage said leaf spring.

2. In combination, a thermostatic actuator including an elongated bimetal strip having a mounted end and a free end; a trigger-equipped snap switch located adjacent the free end of said strip so that back-and-forth movement thereof is effective to move the trigger; first mechanism for adjusting the initial position of said strip to calibrate same for switch-actuating movement in a given temperature range; and a second mechanism for varying the actuation temperature in said range, including a manually rotatable cam and a relatively stiff cam-engaging leaf spring mounted on the bimetal strip.

3. in combination, a probe type control: a casing having a base wall; an elongated probe structure projecting generally right angularly from said base wall and including flange means seated thereagainst; a thermal actuator, including a flat elongated bimetal strip having a portion thereof mounted on a portion of the probe structure remote from the base wall and having a free end thereof projecting through the base wall; a trigger-equipped snap switch seated on the base wall, with the trigger thereof registering with the aforementioned free end so that movement of said free end is effective to actuate the switch; and headed connecter means extending through the aforementioned flange means, base wall and snap switch to secure same together.

4. In combination, a base wall having an opening therein; an elongated support structure extending generally normal to said base wall and having flange means seated thereagainst; a pair of generally parallel bimetal strips having ends thereof mounted on a portion of the support structure remote from the base wall and having free ends thereof projecting through the base wall opening; a pair of trigger-equipped snap switches mounted on the face of the base wall remote from the support structure, with the triggers thereof facing one another and with the free ends of the bimetal strips located therebetween; a generally U-shaped shield structure having a web wall engaging the faces of the snap switches remote from the base wall and having flanges extending to the base wall in the space between said switches; and means for adjusting the operating temperature of one of the switches, including a rotary cam mounted on the aforementioned web wall and a cam-engageable leaf spring mounted on said one bimetal strip.

5. The combination of claim 4 and further comprising a plurality of beaded connecters extending through the base wall, web wall, support structure flanges and switches to secure same together.

6. In combination, a two-piece housing structure including a base section and a cover section rcmovably disposed thereon; said base section comprising a base wall having an opening therein, and said cover section comprising a front wall extending generally parallel to the base wall; an elongated support structure extending generally normal to the base wail away from the cover section front wall; a thermal actuator inciuding two elongated bimetal strips having portions thereof mounted on a portion of the support structure remote from the base wall and having free ends thereof projecting through the base wall opening; a pair of trigger-equipped snap switches mounted on the face of the base wall remote from the support structure, with the triggers thereof facing one another and with the free ends of the bimetal strips lo cated therebetween; a generally U-shaped shield structure having a web wall engaging the faces of the snap switches remote from the base wall and having flanges extending to the base wall in the space between said switches; and means for adjusting the operating temperature of one of the switches, including a rotary cam mounted on the aforementioned web wall and a cam-engageable leaf spring mounted on said one bimetal strip; the aforemen tioned housing section front wall having an opening therethrough, and said rotary cam having a manual actuator extending through said front wall opening so that the cover section can be removed from the base section to expose the switches and shield structure without disturbing the rotary cam.

7. In combination, a two-piece housing structure 1ncluding a base section and a cover section rernovably disposed thereon; said base section comprising a rectangular base wall, end walls projecting from opposite ones of its edges, and flanges projecting from its other edges, said cover section comprising a front Wall extending generally parallel to the base wall, and side walls extending into close telescoping adjacency with inner surfaces of the flanges; said flanges and side walls having cooperating detents and recesses for retaining the cover section in place; an elongated support structure extending generally normal to the base wall away from the cover section front wall; a thermal actuator including two elongated bimetal strips having portions thereof mounted on a portion of the support structure remote from the base wall and having free ends thereof projecting through the base wall opening; a pair of trigger-equipped snap switches mounted on the face of the base wall remote from the support structure, with the triggers thereof facing one another and with the free ends of the bimetal strips located therebetween; a generally U-shaped shield structure having a web wall engaging the faces of the snap switches remote from the base wall and having flanges extending to the base wall in the space between said switches; and means for adjusting the operating temperature of one of the switches, including a rotary cam mounted on the aforementioned web wall and a cam-engageable leaf spring mounted on said one bimetal strip; the aforementioned housing section front wall having an opening therethrough, and said rotary cam having a manual actuator extending through said front wall opening so that the cover section can be removed from the base section to expose the switch and shield structure without disturbing the rotary cam; said switches having terminals thereon, and one of the aforementioned end walls having an opening therethrough for the extension of lead wires to the terminals.

8. In combination, a casing having a base wall; an elongated support structure projecting generally right angularly from said base wall and defining two facing support surfaces adjacent the end thereof located remote from the base wall; a U-shaped bimetal having a relatively short .web extending generally transverse to the facing support surfaces and two relatively long legs extending from the short web toward the aforementioned base Wall, said legs being fixedly secured to the support surfaces at points 7 adjacent the web; a pair of trigger-equipped snap switches ing screws carried on the elongated support structure adjacent the secured portions of the bimetal legs, said screws being independently adjustable and engageable with respective ones of the legs for separately adjusting the position of each leg to thus permit the respective legs to actuate their respective switches in different and widely spaced temperature ranges.

9. In combination, a casing having a base wall; an elongated support channel projecting generally right angularly from said base wall and defining two facing support surfaces in the end thereof located remote from the base wall; a U-shaped bimetal disposed within the support channel, said bimetal having a relatively short web extending generally transverse to the facing support surfaces and two relatively long legs extending from the short web toward the aforementioned base wall, said legs being fixedly secured to the support surfaces at points adjacent the web; a pair of trigger-equipped snap switches arranged within the aforementioned casing with the triggers thereof facing one another so as to be operated by warping movements of the bimetal legs; and two adjusting screws carried on the elongated support channel adjacent the secured portions of the bimetal legs, said screws being independently adjustable and engageable with respective ones of the legs for separately adjusting the position of each leg to thus permit the respective legs to actuate their respec tive switches in different and Widely spaced temperature ranges.

10. In a probe type control: a casing; an elongated probe structure projecting from said casing and defining two facing support surfaces adjacent the end thereof located remote from the casing; a thermal actuator, including two elongated flat bimetal strips having portions thereof fixedly secured to respective ones of the facing support surfaces, said bimetal strips extending from the support surfaces into the aforementioned casing; a pair of switches arranged within the aforementioned casing and having operators thereof facing one another to be operated by warping movements of the bimetal strips; and two adjusting elements located on the elongated probe structure adjacent the secured portions of the bimetal strips, said elements being independently adjustable and engageable with respective ones of the strips for separately adjusting the position of each strip to thus permit the respective strips to actuate their respective switches in different temperature ranges.

11. In a probe type control: a casing; an elongated probe structure projecting from said casing and defining two support surfaces adjacent the end thereof located remote from the casing; a thermal actuator, including two elongated fiat bimetal strips having portions thereof fixedly secured to respective ones of the support surfaces, said bimetal strips extending from the support surfaces into the aforementioned casing; a pair of switches arranged within the aforementioned casing and having operators thereof located to be moved by warping motions of the bimetal strips; and two adjusting elements located on the elongated probe structure adjacent the secured portions of the bimetal strips, said elements being independently adjustable and engageable with respective ones of the strips for separately adjusting the position of each strip to thus permit the respective strips to actuate their respective switches in different temperature ranges.

References Cited in the file of this patent UNITED STATES PATENTS 1,034,689 Chapman Aug. 6, 1912 1,706,057 Duemler et a1 Mar. 19, 1929 1,772,279 Fonseca Aug. 5, 1930 2,087,024 Dezotell July 13, 1937 2,149,085 Crago Feb. 28, 1939 2,374,097 Holmes Apr. 17, 1945 2,611,855 Turner Sept. 23, 1952 2,878,344 Gustafson et al. Mar. 17, 1959 2,985,738 Baak May 23, 1961 

2. IN COMBINATION, A THERMOSTATIC ACTUATOR INCLUDING AN ELONGATED BIMETAL STRIP HAVING A MOUNTED END AND A FREE END; A TRIGGER-EQUIPPED SNAP SWITCH LOCATED ADJACENT THE FREE END OF SAID STRIP SO THAT BACK-AND-FORTH MOVEMENT THEREOF IS EFFECTIVE TO MOVE THE TRIGGER; FIRST MECHANISM FOR ADJUSTING THE INITIAL POSITION OF SAID STRIP TO CALIBRATE SAME FOR SWITCH-ACTUATING MOVEMENT IN A GIVEN TEMPERATURE RANGE; AND A SECOND MECHANISM FOR VARYING THE ACTUATION TEMPERATURE IN SAID RANGE, INCLUDING A MANUALLY ROTATABLE CAM AND A RELATIVELY STIFF CAM-ENGAGING LEAF SPRING MOUNTED ON THE BIMETAL STRIP. 